Conventional armor is subjected to a variety of projectiles designed to defeat the armor by either penetrating the armor with a solid or molten object or by inducing shock waves in the armor that are reflected in a manner to cause spalling of the armor such that an opening is formed and the penetrator (usually stuck to a portion of the armor) passes through, or an inner layer of the armor spalls and is projected at high velocity without physical penetration of the armor.
Some anti-armor weapons are propelled to the outer surface of the armor where a shaped charge is exploded to form a generally linear “jet” of metal that will penetrate solid armor; these are often called Hollow Charge (HC) weapons. A second type of anti-armor weapon uses a linear, heavy metal penetrator projected at high velocity to penetrate the armor. This type of weapon is referred to as EFP (explosive formed projectile) or SFF (self forming fragment) or a “pie charge” or sometimes a “plate charge.”
In some of these weapons the warhead behaves as a hybrid of the HC and the EFP and produces a series of metal penetrators projected in line towards the target. Such a weapon will be referred to herein as a Hybrid warhead. Hybrid warheads behave according to how much “jetting” or HC effect it has and up to how much of a single big penetrator-like an EFP it produces.
Various protection systems are effective at defeating HC jets. Amongst different systems the best known are reactive armors that use explosives in the protection layers that detonate on being hit to break up most of the HC jet before it penetrates the target. The problem is that these explosive systems are poor at defeating EFP or Hybrid systems
Another system has been proposed to defeat such weapons where the armor is comprised of two layers with an electrical conductor disposed therebetween. An significant electric potential is created between the electrical conductor and the adjacent surfaces of the armor. When a liquid or solid penetrator penetrates the armor it creates an electrically conductive path between the armor layers and the electrical conductor through which the electrical potential is discharged. When there is sufficient electrical energy discharged through the penetrator it is melted or vaporized and its ability to penetrate the next layer of armor is significantly reduced.
Another type of anti-armor weapon propels a relatively large, heavy, generally ball-shaped solid projectile (or a series of multiple projectiles) at high velocity. When the ball-shaped metal projectile(s) hits the armor the impact induces shock waves that reflect in a manner such that a plug-like portion of the armor is sheared from the surrounding material and is projected along the path of the metal projectile(s), with the metal projectile(s) attached thereto. Such an occurrence can, obviously, have very significant detrimental effects on the systems and personnel within a vehicle having its armor defeated in such a manner.
While the HC type weapons involve design features and materials that dictate they be manufactured by an entity having technical expertise, the later type of weapons (EFP and Hybrid) can be constructed from materials readily available in a combat area. For that reason, and the fact such weapons are effective, has proved troublesome to vehicles using conventional armor.
The penetration performance for the three mentioned types of warheads is normally described as the ability to penetrate a solid amount of RHA (Rolled Homogeneous Armor) steel armor. Performances typical for the weapon types are: HC warheads may penetrate 1 to 3 ft thickness of RHA, EFP warheads may penetrate 1 to 6 inches of RHA, and Hybrids warheads may penetrate 2 to 12 Inches thick RHA. These estimates are based on the warheads weighing less than 15 lbs and fired at their best respective optimum stand off distances. The diameter of the holes made through the first inch of RHA would be; HC up to an inch diameter hole, EFP up to a 9 inch diameter hole, and Hybrids somewhere in between. The best respective optimum stand off distances for the different charges are: standoff distances for an HC charge is good under 3 feet but at 10 ft or more it is very poor; for an EFP charge a stand off distance up to 30 feet produces almost the same (good) penetration and will only fall off significantly at very large distances like 50 yards; and for Hybrid charges penetration is good at standoff distances up to 10 ft but after 20 feet penetration starts falling off significantly. The way these charges are used are determined by these stand off distances and the manner in which their effectiveness is optimized (e.g. the angles of the trajectory of the penetrator to the armor). These factors effect the design of the protection armor.
The present invention is effective against Hybrid charges because it must be placed close to the edge of the road to provide deep penetration and thus it must be angled upward to hit the desired portion of the target. As a result it does not hit the armor at a right angle to its surface. The jet is therefore at least partially deflected from its trajectory and its penetration is reduced. An effective EFP can hit from a relatively long stand off distance and has a good chance of hitting square on with good penetration but the present invention is very effective against EFPs. The Hybrid and EFP are the threats the invention is intended to address.
While any anti-armor projectile can be defeated by armor of sufficient strength and thickness, extra armor thickness is heavy and expensive, adds weight to any armored vehicle using it which, in turn places greater strain on the vehicle engine, and drive train.
Armor solutions that offer a weight advantage against these types of weapons can be measured in how much weight of RHA it saves when compared with the RHA needed to stop a particular weapon penetrating. This advantage can be calculated as a protection ratio, the ratio being equal to the weight of RHA required to stop the weapon penetrating, divided by the weight of the proposed armor system that will stop the same weapon. Such weights are calculated per unit frontal area presented in the direction of the anticipated trajectory of the weapon.
Thus, there exists a need for an armor that can defeat the projectiles from anti-armor devices without requiring excess thicknesses of armor. Preferably, such armor would be made of material that can be readily fabricated and incorporated into a vehicle design at a reasonable cost, and even more preferably, can be added to existing vehicles.
As the threats against armored vehicles increase and become more diverse, combinations of armor or armor systems are needed to defeat the various threats. The present invention is in addition to the common design features needed to protect the vehicle against military assault rifle bullets, bomb shrapnel and landmine explosions. An armor system that raises the protection level of an armored vehicle to include EFP and Hybrid charges is described.